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Arid Land Geography ›› 2019, Vol. 42 ›› Issue (2): 244-251.doi: 10.12118/j.issn.1000-6060.2019.02.03

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Cloud structure characteristics in heavy snowfall days in northern Xinjiang using Cloudsat satellite data

WANG Zhi-min1,FENG Wan-yue2,LI Yuan-yuan1,CHU Chang-jiang3,XU Wen-xia1,CHENG Yong-hang4   

  1. ( 1  Xinjiang Weather Modification Office,Urumqi 830002,Xinjiang,China;2  Meteorological and Technical Equipment Support Center of Xinjiang Uygur Autonomous Region, Urumqi 830002,Xinjiang,China;3  Xinjiang Meteorological Bureau, Urumqi 830002,Xinjiang,China;
    4  College of Environmental Science and Engineering,Donghua University Shanghai,Shanghai 201620,China)
  • Online:2019-03-25 Published:2019-03-07

Abstract: The CloudSat observational dataset provides an important opportunity to study snowfall, and there have been numerous investigations making use of CloudSat for snowfall-related research. Based on the data of 2B-CLDCLASS, 2B-CWC-RVOD and 2C-SNOW-PROFILE and the precipitation data of the ground observation stations, the macro and micro physical properties of the clouds before and during the snowfall were compared and analyzed in 21 heavy snowfall events in the northern Xinjiang, China. In the paper, the northern Xinjiang was divided into the western and the central region along Tianshan Mountains. Firstly, all the sites which had precipitation reached to heavy snowstorm in 24 hours were selected in the northern Xinjiang from 2008 to 2015. Then, according to the specific dates of the snowfall and the latitude and longitude of the sites, those sites which had CloudSat passed their territory were selected as the research object and there were 21 cases obtained. Out of the 21 cases there were 12 cases with the satellite passing their territories while the snowfall was occurring, and 9 cases with the satellite passing their territories before snowfall. The distributions of microphysical properties, which include ice effective radius (IER), ice number concentration (INC), ice water content (IWC), snow water content (SWC) and snow rate (SR), were revealed through analyzing the clouds, cloud types of heavy snowfall and the relationship between cloud microphysical properties and snowfall. Before the heavy snowfall and during the heavy snowfall, the main cloud types were altostratus clouds, cumulus clouds, nimbostratus, stratus clouds, the convective clouds between altostratus clouds and deep stratus. The maximum of IER was 296.5 μm and the minimum was 28.4 μm. The mean of IER of ice cloud was 64.1 μm before the snowfall, and 62.3 μm in the snowfall. The IER before the snowfall was 7.1 % larger than that in the snowfall. The largest INC is 768.4 L-1, and the values of geometric mean range of INC were 41.2-76.5 L-1 before the snowfall, and 28.1-73.0 L-1 during the snowfall. The values of geometric mean range of IWC of ice cloud were 25.4-135.1 mg·m-3 before the snowfall, and 12.0-77.7 mg·m-3 during the snowfall. The largest IWC was 701.8 mg·m-3, and the smallest IWC was 1.0 mg·m-3. The mean values of SWC and SR were 28.0~88.0 mg·m-3 and 0.08~0.36 mm·h-1 respectively. The mean values of IER, INC, IWC, SWC and SR before the snowfall were respectively 2.9 %, 6.2 %, 34.4 %, 36.4 % and 18.7 % higher than those during the snowfall. The areas with larger values of the micro physical cloud properties are mainly concentrated in the western part of northern Xinjiang. This study had presented a comprehensive analysis of cloud vertical structures and regional variations before and during the heavy snowfall. The analysis of ice effective radius, ice number concentration, ice water content, snow water content and snow rate also helps understand the artificial snow augmentation.

Key words: Cloudsat, heavy snowfall, macro and micro physical properties, northern Xinjiang